QUARTERLY FOCUS ISSUE: HEART RHYTHM DISORDERS
Atrial Fibrillation at Baseline and During Follow-Up in ALLHAT (Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial)
L. Julian Haywood, MD*,
Charles E. Ford, PhD ,*,
Richard S. Crow, MD ,
Barry R. Davis, MD, PhD,
Barry M. Massie, MD ,
Paula T. Einhorn, MD||,
Angela Williard, RN, BSN¶ for the ALLHAT Collaborative Research Group
* Los Angeles County/University of Southern California Medical Center, Los Angeles, California
University of Texas Health Science Center at Houston, School of Public Health, Houston, Texas
University of Minnesota, Minneapolis, Minnesota
San Francisco Veterans Affairs Medical Center, San Francisco, California
|| Division of Prevention and Population Sciences, National Heart, Lung, and Blood Institute, Bethesda, Maryland
¶ Department of Epidemiology, Tulane University School of Public Health and Tropical Medicine, New Orleans, Louisiana
Manuscript received December 22, 2008;
revised manuscript received August 7, 2009,
accepted August 18, 2009.
* Reprint requests and correspondence: Dr. Charles E. Ford, The University of Texas School of Public Health, 1200 Herman Pressler Drive, E-827, Houston, Texas 77030 (Email: charles.e.ford{at}uth.tmc.edu).
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Abstract
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Objectives: The ALLHAT (Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial) determined that treatment with amlodipine, lisinopril, or doxazosin was not superior to thiazide-like diuretic (chlorthalidone) in preventing coronary heart disease (CHD) or other cardiovascular events. This subanalysis examines baseline prevalence and in-trial incidence of new-onset atrial fibrillation (AF) or atrial flutter (AFL) and their influence on clinical outcomes.
Background: Limited information is available on whether atrial fibrillation incidence is affected differentially by different classes of antihypertensive medications or treatment with statins.
Methods: AF/AFL was identified from baseline and follow-up electrocardiograms performed biannually. Analyses were performed to identify characteristics associated with baseline AF/AFL and its subsequent incidence.
Results: AF/AFL was present at baseline in 423 participants (1.1%), more frequent in men (odds ratio: 1.72; 95% confidence interval [CI]: 1.37 to 2.17) and nonblacks (odds ratio: 2.09; 95% CI: 1.58 to 2.75). Its prevalence increased with age (p < 0.001) and was associated with CHD, cardiovascular disease, obesity, and high-density lipoprotein cholesterol <35 mg/dl. New-onset AF/AFL was associated with the same baseline risk factors plus electrocardiogram left ventricular hypertrophy. It occurred in 641 participants (2.0%) and, excluding doxazosin, did not differ by antihypertensive treatment group or, in a subset of participants, by pravastatin versus usual care. Baseline AF/AFL was associated with increased mortality (hazard ratio [HR]: 2.82; 95% CI: 2.36 to 3.37; p < 0.001), stroke (HR: 3.63; 95% CI: 2.72 to 4.86; p < 0.001), heart failure (HR: 3.17; 95% CI: 2.38 to 4.25; p < 0.001), and fatal CHD or nonfatal myocardial infarction (HR: 1.64; 95% CI: 1.22 to 2.21; p < 0.01). There was a nearly 2.5-fold increase in mortality risk when AF/AFL was present at baseline or developed during the trial (HR: 2.42; 95% CI: 2.11 to 2.77; p < 0.001).
Conclusions: In this high-risk hypertensive population, pre-existing and new-onset AF/AFL were associated with increased mortality. Excluding doxazosin, treatment assignment to either antihypertensive drugs or pravastatin versus usual care did not affect AF/AFL incidence. (Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial [ALLHAT]; NCT00000542)
Key Words: hypertension • atrial fibrillation • clinical trial • chlorthalidone • amlodipine • lisinopril • doxazosin • pravastatin
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Abbreviations and Acronyms
| | ACE = angiotensin-converting enzyme | | AF = atrial fibrillation | | AFL = atrial flutter | | ARB = angiotensin receptor blocker | | ASCVD = atherosclerotic cardiovascular disease | | BMI = body mass index | | BP = blood pressure | | CHD = coronary heart disease | | CI = confidence interval | | CVD = cardiovascular disease | | ECG = electrocardiogram | | eGFR = estimated glomerular filtration rate | | HR = hazard ratio | | LVH = left ventricular hypertrophy | | OR = odds ratio | | PH = proportional hazards |
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Atrial fibrillation (AF) is the most common clinically significant cardiac arrhythmia (1–3). It is associated with markedly increased risks of stroke, heart failure, and cardiovascular death (3). Hypertension is the most frequent cause of AF and stroke, and the combination of hypertension and AF is associated with a particularly high stroke risk. The prevalence of AF increases with age. Other risk factors for AF include heart failure, diabetes, left atrial enlargement, left ventricular hypertrophy (LVH), and specific triggers such as hyperthyroidism and excessive alcohol use (3–6). Atrial flutter (AFL) is known to have similar risk factors and outcomes.
In the Framingham Heart Study, AF prevalence increased from 0.5% of individuals age 50 to 59 years to 9% of those 80 to 89 years. Hypertension was associated with a significant 1.8 odds ratio (OR) for developing atrial fibrillation (p < 0.001) and a population-attributable risk of 14% (6). At age 40 years or older, lifetime risk for AF development has been estimated at 25%, with risk for men somewhat higher than for women (7). Data from the ATRIA (Anticoagulation and Risk Factor in Atrial Fibrillation) study and the National Center for Health Statistics suggest that the prevalence of AF may be lower in African Americans despite the higher incidence of stroke and deaths from stroke in this group (8,9).
The ALLHAT (Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial), with 42,418 participants, is the largest clinical trial in a hypertensive population and thus offers an opportunity to investigate the prevalence of AF at baseline in a well-defined hypertensive population and its new appearance during a prolonged follow-up experience (1994 to 2002) (10–14). The high proportion of African Americans (36%) and type 2 diabetic participants (36%) and the older age of the participants (35% ages  70 years) allows assessment of the impact of these characteristics on AF occurrence.
Further, limited information is available on whether AF incidence is affected differentially by different classes of antihypertensive medications or treatment with statins. Recent data have suggested that treatment with angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) may reduce the incidence or recurrence of AF in patients with hypertension, heart failure, LVH on electrocardiogram (ECG), or prior episodes of AF (15–17). ALLHAT participants, randomized to 4 antihypertensive treatment arms, allow comparison of the ability of an ACE inhibitor (lisinopril), a dihydropyridine calcium-channel blocker (amlodipine), and an alpha-adrenoreceptor blocker (doxazosin) relative to a thiazide-like diuretic (chlorthalidone) to prevent incident AF. A subset of participants, randomized to pravastatin or usual care, allows comparison of a statin's ability to prevent incident AF relative to usual care.
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Methods
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The rationale and design of the ALLHAT study have been reported (10). Briefly, ALLHAT was a randomized, double-blind, practice-based, multicenter clinical trial sponsored by the National Heart, Lung, and Blood Institute. It was designed to determine whether the calcium-channel blocker, the ACE inhibitor, or the alpha-blocker was superior to the thiazide-like diuretic in preventing coronary heart disease (CHD) or other cardiovascular disease (CVD) events. A lipid-lowering trial component involved a subset of participants, randomly assigned to open-label pravastatin or usual care (13). Participants were hypertensive men and women 55 years of age with at least 1 additional CVD risk factor (10). Individuals with a history of hospitalized or treated symptomatic heart failure and/or known impaired left ventricular function (ejection fraction <35%) were excluded. Individuals with AF/AFL were not excluded. Blood pressure (BP) eligibility was defined on the basis of the participant's current treatment status and average BP at 2 visits. For untreated participants, average systolic BP had to be in the range of 140 to 180 mm Hg and diastolic, 90 to 100 mm Hg, at both visits. Treated participants had to be on 1 to 2 antihypertensive drugs and have BP  160/100 mm Hg at visit 1 and BP 180/110 mm Hg at visit 2. To maximize statistical power, 1.7 times as many participants were assigned to chlorthalidone than each alternative treatment (18). Participants were recruited at 623 centers in the U.S., Canada, Puerto Rico, and the U.S. Virgin Islands, between February 1994 and January 1998 (19,20). All participants gave written informed consent, and all centers obtained institutional review board approval.
Closeout for the nondoxazosin groups was October 2001 to March 2002 (12). The doxazosin arm was terminated in February 2000 (11), and its follow-up interval (average 3.2 years) differed from the other treatment groups (average 4.9 years). Separate follow-up analyses were done for the doxazosin and nondoxazosin comparisons with chlorthalidone (12,13).
The treatment goal was BP <140/90 mm Hg, achieved by titration of the assigned study drug (step 1) and addition of open-label agents when necessary. Nonpharmacological approaches to treatment of hypertension were recommended according to national guidelines (21,22). Step 1 drug dosages were 12.5, 12.5 (sham titration), and 25 mg/day for chlorthalidone; 2.5, 5, and 10 mg/day for amlodipine; 10, 20, and 40 mg/day for lisinopril, and 2, 4, and 8 mg/day for doxazosin. Additional study-supplied, open-label drugs were also available for BP control, and other drugs, including low doses of open-label step 1 drug classes, were permitted if clearly indicated (10). After initial titration visits, participants were seen every 3 months in year 1 and every 4 months thereafter.
ECG analysis.
ECGs were recorded at clinical sites using standardized procedures at baseline and biannually and forwarded to the ECG Reading Center (University of Minnesota, Minneapolis) (23). Baseline and follow-up ECGs were coded for rhythm, with AF and AFL coded separately using Minnesota Code definitions. In this report, AF and AFL were considered together (AF/AFL).
Statistical methods.
Prevalence rates for AF/AFL were based on baseline ECGs and were directly adjusted for distributional differences in age, race, and sex using the combined ALLHAT population as the standard. Incidence rates for new AF/AFL were based on follow-up ECGs among participants without AF/AFL at baseline. Prevalence and incidence of AF/AFL were tabulated for subgroups defined by demographic and clinical characteristics. Multivariable logistic regression analyses were done to examine the relative odds of AF/AFL prevalence and incidence for the prognostic characteristics. Likewise, AF/AFL incidence by antihypertensive treatment group and for pravastatin versus usual care was compared in multiple logistic analyses, with and without adjustment for relevant covariates.
Cumulative 6-year event rates for CHD, death, stroke, and heart failure were calculated using the Kaplan-Meier procedure. Log-rank tests and Cox proportional hazards (PH) models incorporating the participant's entire trial experience were used to evaluate differences between cumulative event curves and to obtain 2-sided p values. Only the PH results are presented, because p values were essentially identical. Hazard ratios (HRs) and 95% confidence intervals (CIs) were obtained from the PH models (24). To assess risk of death after the development of new AF/AFL or its presence at baseline, a time-dependent PH model was used with a time-varying indicator variable for presence or absence of AF/AFL. In this latter analysis, participants without AF/AFL at baseline remained in the AF/AFL absent risk group until new-onset AF/AFL was ascertained, at which time they were reclassified as AF/AFL present, and participants who died before a follow-up ECG could be obtained were classified as AF/AFL absent.
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Results
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Prevalence of AF/AFL.
Baseline ECGs were available for 92.1% of the 42,418 randomized ALLHAT participants. The proportion of participants missing a baseline ECG (7.8% chlorthalidone, 8.0% amlodipine, 8.2% lisinopril, 7.8% doxazosin) did not differ by treatment group (p = 0.770). However, the proportion without follow-up ECGs (23.3% chlorthalidone, 23.4% amlodipine, 26.0% lisinopril) was higher in the lisinopril group (p < 0.001). The doxazosin group had the highest proportion missing (29.5%), likely due to the early rapid termination of this arm.
Pre-existing AF/AFL was present in 423 (1.1%) of the 39,056 participants evaluated. Of these, only 20 had AFL. The prevalence of AF/AFL was, respectively, 10.5, 11.9, 10.6, and 10.7 per 1,000 participants in the chlorthalidone, lisinopril, amlodipine, and doxazosin groups. These differences were not statistically significant (p = 0.77). Randomization produced well-balanced treatment groups on all variables of prognostic importance (23), and direct adjustment for distributional differences in age, race, and sex did not affect treatment group-specific AF/AFL prevalence rates.
Older, male, and nonblack participants were more likely to have AF/AFL at trial entry (Table 1). Octogenarians had approximately 5-fold greater odds of having AF/AFL than those in their 60s. After adjusting for the other baseline characteristics, AF/AFL prevalence increased by approximately 10% with each year after age 55 years (p < 0.001) (Table 2); men were 1.72 times more likely than women to have AF/AFL (p < 0.001, reciprocal of 0.581) (Table 2); and nonblacks were 2.09 times more likely than blacks (p < 0.001). Baseline mean blood pressure for those with and without AF/AFL was similar (145.6/84.1 mm Hg vs. 146.3/84.0 mm Hg, respectively), but AF/AFL was significantly more prevalent in those with a history of CHD, who were 1.34 times more likely than those without CHD to have AF/AFL (p = 0.011) (Table 2). Those with ASCVD (of which CHD was a component) were also more likely to have AF/AFL than those without ASCVD (p < 0.01) (Table 1). Similarly in adjusted and multivariable analyses, AF/AFL was significantly more prevalent in those not routinely taking aspirin (p < 0.001), in those with body mass index (BMI) 30 kg/m2 (p < 0.001), and with HDL <35 mg/dl (p < 0.01).
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Table 2 Estimated ORs and Corresponding SEs and 95% CIs for Prevalence of AF/AFL at Baseline Among ALLHAT Participants
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AF/AFL was less prevalent in smokers and among diabetics (each an ALLHAT eligibility criterion). This difference was largely due to the younger age distribution of these subgroups compared with their counterparts, and they did not differ significantly in adjusted and multivariable analyses. There was no difference in the adjusted prevalence of AF/AFL when stratified by baseline estimated glomerular filtration rate (eGFR) (25). Although the unadjusted prevalence was statistically greater for those with eGFR <60 ml/min per 1.73 m2, this was largely due to their older age (55% >70 years compared with 31% of those with eGFR 60 ml/min per 1.73 m2).
Incidence of AF/AFL.
Follow-up ECGs were available for 25,332 (76%) of 33,357 participants assigned to chlorthalidone, lisinopril, or amlodipine. New AF/AFL developed in 537 (2.1%) of these participants (32 were AFL). Tables 3 and 4
 present the number of new AF/AFL cases, corresponding crude AF/AFL incidence per 1,000, and ORs for developing AF/AFL. The multiple logistic analyses presented in Table 4 were adjusted for distributional differences in age, race, sex, and pre-existing CHD.
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Table 4 Development of AF/AFL During Follow-Up per 1,000 Participants, Overall and by Major Subgroups (Doxazosin Participants Excluded)
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There were no significant differences in development of new AF/AFL between the chlorthalidone group and the lisinopril or amlodipine groups during follow-up (Table 3), nor between the pravastatin and usual care groups. New-onset AF/AFL was higher in those assigned to doxazosin compared with chlorthalidone (OR: 1.35; p = 0.02). The incidence of AF/AFL did not significantly differ by treatment group within the demographic and clinical subgroups examined (data not shown).
There were differences in new AF/AFL occurrence between strata (Tables 4 and 5). Similar to the baseline prevalence findings, older subjects, men, nonblacks, and those with pre-existing CHD, high BMI, and low HDL had a higher incidence of AF/AFL. Unlike the prevalence data, LVH was associated with a 2-fold greater risk of incident AF/AFL (adjusted OR: 2.11; p < 0.001). In univariate analysis, lower baseline eGFR was associated with a higher risk of incident AF/AFL (30.6 vs. 19.7 per 1,000; p < 0.001). However, as in the prevalence data, this was likely due to the correlation of eGFR with age (–0.308; p < 0.001); in adjusted (multivariable) analysis (Table 4), the OR did not differ significantly from 1.0. Similarly, nonsmokers tended to be older than smokers (p < 0.001) due to the inclusion of smoking as an eligibility criterion, and nonsmoking was not a significant predictor of AF/AFL in the multiple logistic analysis (Table 4). Unlike the prevalence data, participants treated for hypertension before entering the trial (90% of ALLHAT participants) were 50% more likely to develop new AF/AFL. However, prior BP medication use was not significant after adjusting for other prognostic factors (Table 5).
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Table 5 Estimated ORs and Corresponding SEs and 95% CIs for Incidence of AF/AFL Among Nondoxazosin ALLHAT Participants
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Table 5 presents results of multiple logistic regression analysis of new-onset AF/AFL among ALLHAT participants assigned to chlorthalidone, amlodipine, and lisinopril. The OR estimates are presented along with the corresponding 95% CIs and a p value for the statistical test (z-test) that the OR differs from 1.0.
Prognosis of AF/AFL.
Kaplan-Meier cumulative event curves for major clinical outcomes according to baseline AF/AFL status are shown in Figure 1. The hazard ratio (HR) for all-cause mortality was 2.82 (95% CI: 2.36 to 3.37; p < 0.001), with curve divergence beginning early and continuing to trial end (age-sex-race adjusted HR: 2.01; 95% CI: 1.68 to 2.41). For CHD (HR: 1.64; 95% CI: 1.22 to 2.21; p < 0.01), curve separation is not dramatic until year 3, but continues to widen through year 6 (adjusted HR: 1.24; 95% CI: 0.93 to 1.67). The most dramatic outcome related to AF/AFL is the much higher event rate for stroke (HR: 3.63; 95% CI: 2.72 to 4.86; p < 0.001); again, curve separation begins early and continues until trial termination (adjusted HR: 2.84; 95% CI: 2.12 to 3.80). There was also a striking difference in heart failure event rates between groups (HR: 3.17; 95% CI: 2.38 to 4.25; p < 0.001; adjusted HR: 2.35; 95% CI: 1.76 to 3.15).
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Figure 1 Kaplan-Meier Event Curves for All-Cause Mortality, CHD, Stroke, and HF
Kaplan-Meier event curves for all-cause mortality, coronary heart disease (CHD), stroke, and heart failure (HF) among chlorthalidone, amiodipine, and lisinopril participants with atrial fibrillation (AF) or atrial flutter (AFL) at trial entry (n = 334) compared with those without AF/AFL (n = 30,370). CI = confidence interval; MI = myocardial infarction; RR = relative risk (hazard ratio).
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Figure 2
shows cumulative all-cause mortality in participants with AF/AFL at trial entry or occurring during follow-up (n = 821) compared with those without AF/AFL (n = 27,247). Participants who died before a follow-up ECG could be obtained were classified as AF/AFL absent. There was a nearly 2.5-fold increase in the risk of death among those with AF/AFL compared with those without (HR: 2.42; 95% CI: 2.11 to 2.77; p < 0.001). The age-sex-race adjusted HR was 1.86 (95% CI: 1.63 to 2.14; p < 0.001).
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Figure 2 Kaplan-Meier Cumulative Event Curves for All-Cause Mortality
Kaplan-Meier cumulative event curves for all-cause mortality in chlorthalidone, amiodipine, and lisinopril participants with AF/AFL at trial entry or occurring during follow-up (n = 821) compared with mortality in those without AF/AFL (n = 27,247). In this time-dependent analysis, participants without AF/AFL at baseline remained in the AF/AFL absent risk group until new-onset AF/AFL was ascertained, at which time they were reclassified as AF/AFL present. Participants who died before a follow-up electrocardiogram could be obtained were classified as AF/AFL absent. Abbreviations as in Figure 1.
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Discussion
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The prevalence of AF/AFL in ALLHAT baseline ECGs was 10.8 per 1,000. As expected from previous studies, the prevalence increased with age and was higher in men and obese individuals. However, in this hypertensive cohort, neither diabetes nor cigarette smoking was associated with increased risk of AF/AFL. The lower prevalence of AF/AFL in black versus nonblack ALLHAT participants is consistent with data from the ATRIA study and national mortality data (8,9). A study of racial differences in AF prevalence among males followed in the Department of Veterans Affairs health system yielded similar findings, although ECG confirmation of AF was not available (26,27). The EPOCH (Epidemiology, Practice, Outcomes, and Costs of Heart Failure) study further documents a significantly lower (49%) adjusted OR for AF/AFL among African-American heart failure patients compared with Caucasians (28).
Baseline prevalence of AF/AFL in the 4 ALLHAT randomized treatment groups was not associated with differential significance of the baseline risk descriptors. During follow-up, the incidence of new AF/AFL in chlorthalidone, amlodipine, and lisinopril participants (21.2 per 1,000 overall) did not differ significantly among treatment groups. Factors favoring development of new-onset AF/AFL were similar to those associated with baseline prevalence, including older age, male sex, nonblack race, CHD, arteriosclerotic CVD, LVH, BMI 30 kg/m2, and HDL <35 mg/dl. The observed higher unadjusted incidence of AF/AFL in participants with worse renal function was largely explained by adjusting for age. Hypokalemia did not emerge as a prognostic factor in the incidence of AF/AFL.
AF/AFL prevalence and incidence during follow-up were strongly related to participant outcomes in the ALLHAT trial. AF/AFL at baseline was associated with an almost 3-fold increase in all-cause mortality during follow-up (HR: 2.82; p < 0.001), a 3.5-fold increase in the occurrence of stroke, a 3-fold increase in new-onset heart failure, and a substantial increase in the occurrence of fatal CHD or nonfatal myocardial infarction (HR: 1.64; p < 0.01). Notably, the 6-year incidence rates for fatal and nonfatal stroke in the ALLHAT trial were higher for the black population compared with nonblacks (6.6% vs. 5.5%) despite substantially less AF/AFL, suggesting that factors other than AF/AFL are responsible for the high stroke rates in this group (29).
Despite suggestions in the literature of a favorable effect of ACE inhibitors on the likelihood of new-onset AF, no differences in the incidence of AF/AFL were observed between the treatment groups in this study (15–17). This may reflect the limited prospective data in hypertensive patients upon which the earlier conclusions were based, or the lesser blood pressure reduction in the lisinopril group in the ALLHAT trial, or possibly low statistical power to detect such an effect.
Whether blockade of the renin-angiotensin system by an angiotensin II receptor blocker (ARB) would have been more effective than lisinopril could not be determined in the ALLHAT trial. A review of ARB effectiveness in hypertension and heart failure trials summarizes possible mechanisms but does not conclude that ARBs are better than ACE inhibitors for AF prevention (30). LIFE (Losartan Intervention for End Point Reduction in Hypertension) and VALUE (Valsartan Antihypertensive Long-Term Use Evaluation) hypertension trials reported significant decreases in AF rates for losartan compared with atenolol and valsartan compared with amlodipine, respectively. In heart failure trials, candesartan reduced new-onset AF compared with placebo (CHARM [Candesartan in Heart failure: Assessment of Reduction in Mortality and morbidity]), whereas valsartan compared with placebo was ineffective in the participants in Val-HeFT (Valsartan Heart Failure Trial), 92% of whom were being concurrently treated with an ACE inhibitor (17,31–33). In the LIFE trial, the risk of stroke was significantly reduced in the losartan group (17). In the ALLHAT trial, there was a higher risk of stroke in black participants assigned to lisinopril, whereas the risk of new-onset AF/AFL was lower in black versus nonblack participants.
There has been considerable interest in whether the incidence or recurrence of AF is lessened by treatment with statins. Most published studies have been post-hoc observational analyses or secondary analyses from trials with other end points (34,35). The presumed mechanism of such an effect, if present, is prevention or reversal of atrial fibrosis, which has been increased in animal models and patients with atrial fibrillation. However, as has proven to be the case with renin-angiotensin-aldosterone system inhibitors, there has been no clear evidence of a preventative effect of statins in large, well-designed randomized clinical trials of statins. The findings from ALLHAT add importantly to this literature, in that this is one of the largest cohorts of patients with multiple risk factors for developing AF (chronic hypertension, older age, and coronary risk factors) prospectively randomized to a statin with long-term follow-up. The finding that pravastatin treatment was not associated with a lower incidence of AF raises doubt regarding the validity of this hypothesis and certainly mandates further rigorous study before these agents can be recommended for prevention of AF.
New-onset of AF/AFL during follow-up was shown to carry a mortality risk at least as high as that among participants with pre-existing AF/AFL. The 6-year mortality rate among those with pre-existing or new-onset AF/AFL was 42% compared with 40% among those with pre-existing AF/AFL. However, the mean time to new AF/AFL was 3.6 years, allowing significantly less additional years of follow-up for mortality among this group as compared with those with AF/AFL at baseline. Further analyses are needed to explore differences between mortality risk associated with pre-existing and new-onset AF/AFL.
The findings reported here are of great significance because of the marked effect of AF/AFL on the outcomes of patients despite aggressive treatment in the ALLHAT trial and the associated interplay of unalterable risk factors such as age, race, and sex. Thus, aggressive management of AF/AFL according to existing guidelines, including use of anticoagulation, should be integrated into the management of hypertension. Awareness of the increased risk of these patients may warrant closer follow-up and more aggressive management of other risk factors. Similarly, the higher risk of AF/AFL in participants with CHD, LVH, and BMI 30 kg/m2 suggests that prevention and treatment of risk factors, including obesity, might prevent AF.
Study strengths and limitations.
Evaluation of AF/AFL was an ancillary study to ALLHAT, pre-specified early in the trial, but not included in the protocol. Data are not available to assess to what extent the management of AF/AFL in ALLHAT participants met current recommendations or whether adjustments in management or earlier detection might have affected results. As with prior longitudinal studies documenting AF risks, the use of anticoagulation agents was not closely monitored, and adjustment for their use was not possible. AF/AFL incidence could not be ascertained in 8,000 ALLHAT participants leaving the exact magnitude of the AF/AFL incidence uncertain, although missing observations were similar across treatment groups. With an overall rate of 2.1%, large effect sizes would have been necessary to detect something with adequate power, and the ALLHAT trial was not designed for this purpose. Future longitudinal studies involving similar patient populations should consider the potential for outcome results to be altered by the presence of AF at baseline or its occurrence during follow-up. The large number of black participants in the ALLHAT trial was a major asset in validating the lower prevalence and incidence of AF in blacks. Failure to find differential AF/AFL occurrence rates by treatment assignment in this large, randomized trial raises questions regarding whether previous studies suggesting lower new-onset AF/AFL rates with ACE inhibitors or ARBs are generalizable.
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Conclusions
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ALLHAT, the largest prospective, randomized hypertension treatment trial, afforded the opportunity to examine the influence of AF at baseline and its appearance during follow-up on outcomes in the trial. Several striking findings were observed, including the lower prevalence and incidence of AF in black participants, the lack of difference by treatment group (except for doxazosin) on the incidence of new-onset AF, and the marked increase in risk for fatal and major nonfatal cardiovascular outcomes. These results underscore the importance of prevention, early detection, and appropriate management of AF in hypertensive patients, in addition to aggressive BP control. Further studies are indicated to determine whether the application of specific AF management guidelines might alter outcome in specific populations.
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Acknowledgments
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A complete list of members of the ALLHAT Collaborative Research Group has been previously published (12).
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Footnotes
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This research was supported by Health and Human Services contract number N01-HC-35130 from the National Heart, Lung, and Blood Institute, National Institutes of Health, U.S. Department of Health and Human Services, Bethesda, Maryland. Additional financial support was provided by Pfizer, Inc. Study medications were supplied by Pfizer, Inc. (amlodipine and doxazosin), AstraZeneca (atenolol and lisinopril), and Bristol-Myers Squibb (pravastatin). Dr. Davis is on the Data Safety Monitoring Board of Takeda Pharmaceuticals.
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References
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